<?php
    /**
     * @author Gasper Kozak
     * @copyright 2007-2011

     **/

    /**
     * Thrown when an invalid dimension is passed for some operations.
     */
    class WideImage_InvalidImageDimensionException extends WideImage_Exception
    {
    }

    /**
     * Thrown when an image can't be saved (returns false by the mapper).
     */
    class WideImage_UnknownErrorWhileMappingException extends WideImage_Exception
    {
    }

    /**
     * Base class for images.
     */
    abstract class WideImage_Image
    {
        /**
         * Holds the image resource.
         *
         * @var resource
         */
        protected $handle = null;

        /**
         * Flag that determines if WideImage should call imagedestroy() upon object destruction.
         *
         * @var bool
         */
        protected $handleReleased = false;

        /**
         * Canvas object.
         *
         * @var WideImage_Canvas
         */
        protected $canvas = null;

        /**
         * @var string
         */
        protected $sdata = null;

        /**
         * The base class constructor.
         *
         * @param resource $handle Image handle (GD2 resource)
         */
        public function __construct($handle)
        {
            WideImage::assertValidImageHandle($handle);
            $this->handle = $handle;
        }

        /**
         * Cleanup.
         *
         * Destroys the handle via WideImage_Image::destroy() when called by the GC.
         */
        public function __destruct()
        {
            $this->destroy();
        }

        /**
         * This method destroy the image handle, and releases the image resource.
         *
         * After this is called, the object doesn't hold a valid image any more.
         * No operation should be called after that.
         */
        public function destroy()
        {
            if ($this->isValid() && !$this->handleReleased) {
                imagedestroy($this->handle);
            }

            $this->handle = null;
        }

        /**
         * Returns the GD image resource.
         *
         * @return resource GD image resource
         */
        public function getHandle()
        {
            return $this->handle;
        }

        /**
         * @return bool True, if the image object holds a valid GD image, false otherwise
         */
        public function isValid()
        {
            return WideImage::isValidImageHandle($this->handle);
        }

        /**
         * Releases the handle.
         */
        public function releaseHandle()
        {
            $this->handleReleased = true;
        }

        /**
         * Saves an image to a file.
         *
         * The file type is recognized from the $uri. If you save to a GIF8, truecolor images
         * are automatically converted to palette.
         *
         * This method supports additional parameters: quality (for jpeg images) and
         * compression quality and filters (for png images). See http://www.php.net/imagejpeg and
         * http://www.php.net/imagepng for details.
         *
         * Examples:
         * <code>
         * // save to a GIF
         * $image->saveToFile('image.gif');
         *
         * // save to a PNG with compression=7 and no filters
         * $image->saveToFile('image.png', 7, PNG_NO_FILTER);
         *
         * // save to a JPEG with quality=80
         * $image->saveToFile('image.jpg', 80);
         *
         * // save to a JPEG with default quality=100
         * $image->saveToFile('image.jpg');
         * </code>
         *
         * @param string $uri File location
         */
        public function saveToFile($uri)
        {
            $mapper = WideImage_MapperFactory::selectMapper($uri, null);
            $args   = func_get_args();
            array_unshift($args, $this->getHandle());
            $res = call_user_func_array([$mapper, 'save'], $args);
            if (!$res) {
                throw new WideImage_UnknownErrorWhileMappingException(get_class($mapper)." returned an invalid result while saving to $uri");
            }
        }

        /**
         * Returns binary string with image data in format specified by $format.
         *
         * Additional parameters may be passed to the function. See WideImage_Image::saveToFile() for more details.
         *
         * @param string $format The format of the image
         *
         * @return string The binary image data in specified format
         */
        public function asString($format)
        {
            ob_start();
            $args    = func_get_args();
            $args[0] = null;
            array_unshift($args, $this->getHandle());

            $mapper = WideImage_MapperFactory::selectMapper(null, $format);
            $res    = call_user_func_array([$mapper, 'save'], $args);
            if (!$res) {
                throw new WideImage_UnknownErrorWhileMappingException(get_class($mapper).' returned an invalid result while writing the image data');
            }

            return ob_get_clean();
        }

        /**
         * Output a header to browser.
         *
         * @param $name Name of the header
         * @param $data Data
         */
        protected function writeHeader($name, $data)
        {
            header($name.': '.$data);
        }

        /**
         * Outputs the image to browser.
         *
         * Sets headers Content-length and Content-type, and echoes the image in the specified format.
         * All other headers (such as Content-disposition) must be added manually.
         *
         * Example:
         * <code>
         * WideImage::load('image1.png')->resize(100, 100)->output('gif');
         * </code>
         *
         * @param string $format Image format
         */
        public function output($format)
        {
            $args = func_get_args();
            $data = call_user_func_array([$this, 'asString'], $args);

            $this->writeHeader('Content-length', strlen($data));
            $this->writeHeader('Content-type', WideImage_MapperFactory::mimeType($format));
            echo $data;
        }

        /**
         * @return int Image width
         */
        public function getWidth()
        {
            return imagesx($this->handle);
        }

        /**
         * @return int Image height
         */
        public function getHeight()
        {
            return imagesy($this->handle);
        }

        /**
         * Allocate a color by RGB values.
         *
         * @param mixed $R Red-component value or an RGB array (with red, green, blue keys)
         * @param int   $G If $R is int, this is the green component
         * @param int   $B If $R is int, this is the blue component
         *
         * @return int Image color index
         */
        public function allocateColor($R, $G = null, $B = null)
        {
            if (is_array($R)) {
                return imagecolorallocate($this->handle, $R['red'], $R['green'], $R['blue']);
            } else {
                return imagecolorallocate($this->handle, $R, $G, $B);
            }
        }

        /**
         * @return bool True if the image is transparent, false otherwise
         */
        public function isTransparent()
        {
            return $this->getTransparentColor() >= 0;
        }

        /**
         * @return int Transparent color index
         */
        public function getTransparentColor()
        {
            return imagecolortransparent($this->handle);
        }

        /**
         * Sets the current transparent color index. Only makes sense for palette images (8-bit).
         *
         * @param int $color Transparent color index
         */
        public function setTransparentColor($color)
        {
            return imagecolortransparent($this->handle, $color);
        }

        /**
         * Returns a RGB array of the transparent color or null if none.
         *
         * @return mixed Transparent color RGBA array
         */
        public function getTransparentColorRGB()
        {
            $total = imagecolorstotal($this->handle);
            $tc    = $this->getTransparentColor();

            if ($tc >= $total && $total > 0) {
                return null;
            } else {
                return $this->getColorRGB($tc);
            }
        }

        /**
         * Returns a RGBA array for pixel at $x, $y.
         *
         * @param int $x
         * @param int $y
         *
         * @return array RGB array
         */
        public function getRGBAt($x, $y)
        {
            return $this->getColorRGB($this->getColorAt($x, $y));
        }

        /**
         * Writes a pixel at the designated coordinates.
         *
         * Takes an associative array of colours and uses getExactColor() to
         * retrieve the exact index color to write to the image with.
         *
         * @param int   $x
         * @param int   $y
         * @param array $color
         */
        public function setRGBAt($x, $y, $color)
        {
            $this->setColorAt($x, $y, $this->getExactColor($color));
        }

        /**
         * Returns a color's RGB.
         *
         * @param int $colorIndex Color index
         *
         * @return mixed RGBA array for a color with index $colorIndex
         */
        public function getColorRGB($colorIndex)
        {
            return imagecolorsforindex($this->handle, $colorIndex);
        }

        /**
         * Returns an index of the color at $x, $y.
         *
         * @param int $x
         * @param int $y
         *
         * @return int Color index for a pixel at $x, $y
         */
        public function getColorAt($x, $y)
        {
            return imagecolorat($this->handle, $x, $y);
        }

        /**
         * Set the color index $color to a pixel at $x, $y.
         *
         * @param int $x
         * @param int $y
         * @param int $color Color index
         */
        public function setColorAt($x, $y, $color)
        {
            return imagesetpixel($this->handle, $x, $y, $color);
        }

        /**
         * Returns closest color index that matches the given RGB value. Uses
         * PHP's imagecolorclosest().
         *
         * @param mixed $R Red or RGBA array
         * @param int   $G Green component (or null if $R is an RGB array)
         * @param int   $B Blue component (or null if $R is an RGB array)
         *
         * @return int Color index
         */
        public function getClosestColor($R, $G = null, $B = null)
        {
            if (is_array($R)) {
                return imagecolorclosest($this->handle, $R['red'], $R['green'], $R['blue']);
            } else {
                return imagecolorclosest($this->handle, $R, $G, $B);
            }
        }

        /**
         * Returns the color index that exactly matches the given RGB value. Uses
         * PHP's imagecolorexact().
         *
         * @param mixed $R Red or RGBA array
         * @param int   $G Green component (or null if $R is an RGB array)
         * @param int   $B Blue component (or null if $R is an RGB array)
         *
         * @return int Color index
         */
        public function getExactColor($R, $G = null, $B = null)
        {
            if (is_array($R)) {
                return imagecolorexact($this->handle, $R['red'], $R['green'], $R['blue']);
            } else {
                return imagecolorexact($this->handle, $R, $G, $B);
            }
        }

        /**
         * Copies transparency information from $sourceImage. Optionally fills
         * the image with the transparent color at (0, 0).
         *
         * @param object $sourceImage
         * @param bool   $fill        True if you want to fill the image with transparent color
         */
        public function copyTransparencyFrom($sourceImage, $fill = true)
        {
            if ($sourceImage->isTransparent()) {
                $rgba = $sourceImage->getTransparentColorRGB();
                if ($rgba === null) {
                    return;
                }

                if ($this->isTrueColor()) {
                    $rgba['alpha'] = 127;
                    $color         = $this->allocateColorAlpha($rgba);
                } else {
                    $color = $this->allocateColor($rgba);
                }

                $this->setTransparentColor($color);
                if ($fill) {
                    $this->fill(0, 0, $color);
                }
            }
        }

        /**
         * Fill the image at ($x, $y) with color index $color.
         *
         * @param int $x
         * @param int $y
         * @param int $color
         */
        public function fill($x, $y, $color)
        {
            return imagefill($this->handle, $x, $y, $color);
        }

        /**
         * Used internally to create Operation objects.
         *
         * @param string $name
         *
         * @return object
         */
        protected function getOperation($name)
        {
            return WideImage_OperationFactory::get($name);
        }

        /**
         * Returns the image's mask.
         *
         * Mask is a greyscale image where the shade defines the alpha channel (black = transparent, white = opaque).
         *
         * For opaque images (JPEG), the result will be white. For images with single-color transparency (GIF, 8-bit PNG),
         * the areas with the transparent color will be black. For images with alpha channel transparenct,
         * the result will be alpha channel.
         *
         * @return WideImage_Image An image mask
         **/
        public function getMask()
        {
            return $this->getOperation('GetMask')->execute($this);
        }

        /**
         * Resize the image to given dimensions.
         *
         * $width and $height are both smart coordinates. This means that you can pass any of these values in:
         *   - positive or negative integer (100, -20, ...)
         *   - positive or negative percent string (30%, -15%, ...)
         *   - complex coordinate (50% - 20, 15 + 30%, ...)
         *
         * If $width is null, it's calculated proportionally from $height, and vice versa.
         *
         * Example (resize to half-size):
         * <code>
         * $smaller = $image->resize('50%');
         *
         * $smaller = $image->resize('100', '100', 'inside', 'down');
         * is the same as
         * $smaller = $image->resizeDown(100, 100, 'inside');
         * </code>
         *
         * @param mixed  $width  The new width (smart coordinate), or null
         * @param mixed  $height The new height (smart coordinate), or null
         * @param string $fit    'inside', 'outside', 'fill'
         * @param string $scale  'down', 'up', 'any'
         *
         * @return WideImage_Image The resized image
         */
        public function resize($width = null, $height = null, $fit = 'inside', $scale = 'any')
        {
            return $this->getOperation('Resize')->execute($this, $width, $height, $fit, $scale);
        }

        /**
         * Same as WideImage_Image::resize(), but the image is only applied if it is larger then the given dimensions.
         * Otherwise, the resulting image retains the source's dimensions.
         *
         * @param int    $width  New width, smart coordinate
         * @param int    $height New height, smart coordinate
         * @param string $fit    'inside', 'outside', 'fill'
         *
         * @return WideImage_Image resized image
         */
        public function resizeDown($width = null, $height = null, $fit = 'inside')
        {
            return $this->resize($width, $height, $fit, 'down');
        }

        /**
         * Same as WideImage_Image::resize(), but the image is only applied if it is smaller then the given dimensions.
         * Otherwise, the resulting image retains the source's dimensions.
         *
         * @param int    $width  New width, smart coordinate
         * @param int    $height New height, smart coordinate
         * @param string $fit    'inside', 'outside', 'fill'
         *
         * @return WideImage_Image resized image
         */
        public function resizeUp($width = null, $height = null, $fit = 'inside')
        {
            return $this->resize($width, $height, $fit, 'up');
        }

        /**
         * Rotate the image for angle $angle clockwise.
         *
         * Preserves transparency. Has issues when saving to a BMP.
         *
         * @param int  $angle             Angle in degrees, clock-wise
         * @param int  $bgColor           color of the new background
         * @param bool $ignoreTransparent
         *
         * @return WideImage_Image The rotated image
         */
        public function rotate($angle, $bgColor = null, $ignoreTransparent = true)
        {
            return $this->getOperation('Rotate')->execute($this, $angle, $bgColor, $ignoreTransparent);
        }

        /**
         * This method lays the overlay (watermark) on the image.
         *
         * Hint: if the overlay is a truecolor image with alpha channel, you should leave $pct at 100.
         *
         * This operation supports alignment notation in coordinates:
         * <code>
         * $watermark = WideImage::load('logo.gif');
         * $base = WideImage::load('picture.jpg');
         * $result = $base->merge($watermark, "right - 10", "bottom - 10", 50);
         * // applies a logo aligned to bottom-right corner with a 10 pixel margin
         * </code>
         *
         * @param WideImage_Image $overlay The overlay image
         * @param mixed           $left    Left position of the overlay, smart coordinate
         * @param mixed           $top     Top position of the overlay, smart coordinate
         * @param int             $pct     The opacity of the overlay
         *
         * @return WideImage_Image The merged image
         */
        public function merge($overlay, $left = 0, $top = 0, $pct = 100)
        {
            return $this->getOperation('Merge')->execute($this, $overlay, $left, $top, $pct);
        }

        /**
         * Resizes the canvas of the image, but doesn't scale the content of the image.
         *
         * This operation creates an empty canvas with dimensions $width x $height, filled with
         * background color $bg_color and draws the original image onto it at position [$pos_x, $pos_y].
         *
         * Arguments $width, $height, $pos_x and $pos_y are all smart coordinates. $width and $height are
         * relative to the current image size, $pos_x and $pos_y are relative to the newly calculated
         * canvas size. This can be confusing, but it makes sense. See the example below.
         *
         * The example below loads a 100x150 image and then resizes its canvas to 200% x 100%+20
         * (which evaluates to 200x170). The image is placed at position [10, center+20], which evaluates to [10, 30].
         * <code>
         * $image = WideImage::load('someimage.jpg'); // 100x150
         * $white = $image->allocateColor(255, 255, 255);
         * $image->resizeCanvas('200%', '100% + 20', 10, 'center+20', $white);
         * </code>
         *
         * The parameter $merge defines whether the original image should be merged onto the new canvas.
         * This means it blends transparent color and alpha colors into the background color. If set to false,
         * the original image is just copied over, preserving the transparency/alpha information.
         *
         * You can set the $scale parameter to limit when to resize the canvas. For example, if you want
         * to resize the canvas only if the image is smaller than the new size, but leave the image intact
         * if it's larger, set it to 'up'. Likewise, if you want to shrink the canvas, but don't want to
         * change images that are already smaller, set it to 'down'.
         *
         * @param mixed  $width    Width of the new canvas (smart coordinate, relative to current image width)
         * @param mixed  $height   Height of the new canvas (smart coordinate, relative to current image height)
         * @param mixed  $pos_x    x-position of the image (smart coordinate, relative to the new width)
         * @param mixed  $pos_y    y-position of the image (smart coordinate, relative to the new height)
         * @param int    $bg_color Background color (created with allocateColor or allocateColorAlpha), defaults to null (tries to use a transparent color)
         * @param string $scale    Possible values: 'up' (enlarge only), 'down' (downsize only), 'any' (resize precisely to $width x $height). Defaults to 'any'
         * @param bool   $merge    Merge the original image (flatten alpha channel and transparency) or copy it over (preserve). Defaults to false
         *
         * @return WideImage_Image The resulting image with resized canvas
         */
        public function resizeCanvas($width, $height, $pos_x, $pos_y, $bg_color = null, $scale = 'any', $merge = false)
        {
            return $this->getOperation('ResizeCanvas')->execute($this, $width, $height, $pos_x, $pos_y, $bg_color, $scale, $merge);
        }

        /**
         * Returns an image with round corners.
         *
         * You can either set the corners' color or set them transparent.
         *
         * Note on $smoothness: 1 means jagged edges, 2 is much better, more than 4 doesn't noticeably improve the quality.
         * Rendering becomes increasingly slower if you increase smoothness.
         *
         * Example:
         * <code>
         * $nice = $ugly->roundCorners(20, $ugly->allocateColor(255, 0, 0), 2);
         * </code>
         *
         * Use $corners parameter to specify which corners to draw rounded. Possible values are
         * WideImage::SIDE_TOP_LEFT, WideImage::SIDE_TOP,
         * WideImage::SIDE_TOP_RIGHT, WideImage::SIDE_RIGHT,
         * WideImage::SIDE_BOTTOM_RIGHT, WideImage::SIDE_BOTTOM,
         * WideImage::SIDE_BOTTOM_LEFT, WideImage::SIDE_LEFT, and WideImage::SIDE_ALL.
         * You can specify any combination of corners with a + operation, see example below.
         *
         * Example:
         * <code>
         * $white = $image->allocateColor(255, 255, 255);
         * $diagonal_corners = $image->roundCorners(15, $white, 2, WideImage::SIDE_TOP_LEFT + WideImage::SIDE_BOTTOM_RIGHT);
         * $right_corners = $image->roundCorners(15, $white, 2, WideImage::SIDE_RIGHT);
         * </code>
         *
         * @param int $radius     Radius of the corners
         * @param int $color      The color of corners. If null, corners are rendered transparent (slower than using a solid color)
         * @param int $smoothness Specify the level of smoothness. Suggested values from 1 to 4
         * @param int $corners    Specify which corners to draw (defaults to WideImage::SIDE_ALL = all corners)
         *
         * @return WideImage_Image The resulting image with round corners
         */
        public function roundCorners($radius, $color = null, $smoothness = 2, $corners = 255)
        {
            return $this->getOperation('RoundCorners')->execute($this, $radius, $color, $smoothness, $corners);
        }

        /**
         * Returns an image with applied mask.
         *
         * A mask is a grayscale image, where the shade determines the alpha channel. Black is fully transparent
         * and white is fully opaque.
         *
         * @param WideImage_Image $mask The mask image, greyscale
         * @param mixed           $left Left coordinate, smart coordinate
         * @param mixed           $top  Top coordinate, smart coordinate
         *
         * @return WideImage_Image The resulting image
         **/
        public function applyMask($mask, $left = 0, $top = 0)
        {
            return $this->getOperation('ApplyMask')->execute($this, $mask, $left, $top);
        }

        /**
         * Applies a filter.
         *
         * @param int $filter One of the IMG_FILTER_* constants
         * @param int $arg1
         * @param int $arg2
         * @param int $arg3
         * @param int $arg4
         *
         * @return WideImage_Image
         */
        public function applyFilter($filter, $arg1 = null, $arg2 = null, $arg3 = null, $arg4 = null)
        {
            return $this->getOperation('ApplyFilter')->execute($this, $filter, $arg1, $arg2, $arg3, $arg4);
        }

        /**
         * Applies convolution matrix with imageconvolution().
         *
         * @param array $matrix
         * @param float $div
         * @param float $offset
         *
         * @return WideImage_Image
         */
        public function applyConvolution($matrix, $div, $offset)
        {
            return $this->getOperation('ApplyConvolution')->execute($this, $matrix, $div, $offset);
        }

        /**
         * Returns a cropped rectangular portion of the image.
         *
         * If the rectangle specifies area that is out of bounds, it's limited to the current image bounds.
         *
         * Examples:
         * <code>
         * $cropped = $img->crop(10, 10, 150, 200); // crops a 150x200 rect at (10, 10)
         * $cropped = $img->crop(-100, -50, 100, 50); // crops a 100x50 rect at the right-bottom of the image
         * $cropped = $img->crop('25%', '25%', '50%', '50%'); // crops a 50%x50% rect from the center of the image
         * </code>
         *
         * This operation supports alignment notation in left/top coordinates.
         * Example:
         * <code>
         * $cropped = $img->crop("right", "bottom", 100, 200); // crops a 100x200 rect from right bottom
         * $cropped = $img->crop("center", "middle", 50, 30); // crops a 50x30 from the center of the image
         * </code>
         *
         * @param mixed $left   Left-coordinate of the crop rect, smart coordinate
         * @param mixed $top    Top-coordinate of the crop rect, smart coordinate
         * @param mixed $width  Width of the crop rect, smart coordinate
         * @param mixed $height Height of the crop rect, smart coordinate
         *
         * @return WideImage_Image The cropped image
         **/
        public function crop($left = 0, $top = 0, $width = '100%', $height = '100%')
        {
            return $this->getOperation('Crop')->execute($this, $left, $top, $width, $height);
        }

        /**
         * Performs an auto-crop on the image.
         *
         * The image is auto-cropped from each of four sides. All sides are
         * scanned for pixels that differ from $base_color for more than
         * $rgb_threshold in absolute RGB difference. If more than $pixel_cutoff
         * differentiating pixels are found, that line is considered to be the crop line for the side.
         * If the line isn't different enough, the algorithm procedes to the next line
         * towards the other edge of the image.
         *
         * When the crop rectangle is found, it's enlarged by the $margin value on each of the four sides.
         *
         * @param int $margin        Margin for the crop rectangle, can be negative
         * @param int $rgb_threshold RGB difference which still counts as "same color"
         * @param int $pixel_cutoff  How many pixels need to be different to mark a cut line
         * @param int $base_color    The base color index. If none specified (or null given), left-top pixel is used
         *
         * @return WideImage_Image The cropped image
         */
        public function autoCrop($margin = 0, $rgb_threshold = 0, $pixel_cutoff = 1, $base_color = null)
        {
            return $this->getOperation('AutoCrop')->execute($this, $margin, $rgb_threshold, $pixel_cutoff, $base_color);
        }

        /**
         * Returns a negative of the image.
         *
         * This operation differs from calling WideImage_Image::applyFilter(IMG_FILTER_NEGATIVE), because it's 8-bit and transparency safe.
         * This means it will return an 8-bit image, if the source image is 8-bit. If that 8-bit image has a palette transparency,
         * the resulting image will keep transparency.
         *
         * @return WideImage_Image negative of the image
         */
        public function asNegative()
        {
            return $this->getOperation('AsNegative')->execute($this);
        }

        /**
         * Returns a grayscale copy of the image.
         *
         * @return WideImage_Image grayscale copy
         **/
        public function asGrayscale()
        {
            return $this->getOperation('AsGrayscale')->execute($this);
        }

        /**
         * Returns a mirrored copy of the image.
         *
         * @return WideImage_Image Mirrored copy
         **/
        public function mirror()
        {
            return $this->getOperation('Mirror')->execute($this);
        }

        /**
         * Applies the unsharp filter.
         *
         * @param float $amount
         * @param float $radius
         * @param float $threshold
         *
         * @return WideImage_Image Unsharpened copy of the image
         **/
        public function unsharp($amount, $radius, $threshold)
        {
            return $this->getOperation('Unsharp')->execute($this, $amount, $radius, $threshold);
        }

        /**
         * Returns a flipped (mirrored over horizontal line) copy of the image.
         *
         * @return WideImage_Image Flipped copy
         **/
        public function flip()
        {
            return $this->getOperation('Flip')->execute($this);
        }

        /**
         * Corrects gamma on the image.
         *
         * @param float $inputGamma
         * @param float $outputGamma
         *
         * @return WideImage_Image Image with corrected gamma
         **/
        public function correctGamma($inputGamma, $outputGamma)
        {
            return $this->getOperation('CorrectGamma')->execute($this, $inputGamma, $outputGamma);
        }

        /**
         * Adds noise to the image.
         *
         * @author Tomasz Kapusta
         *
         * @param int    $amount Number of noise pixels to add
         * @param string $type   Type of noise 'salt&pepper', 'color' or 'mono'
         *
         * @return WideImage_Image Image with noise added
         **/
        public function addNoise($amount, $type)
        {
            return $this->getOperation('AddNoise')->execute($this, $amount, $type);
        }

        /**
         * Used internally to execute operations.
         *
         * @param string $name
         * @param array  $args
         *
         * @return WideImage_Image
         */
        public function __call($name, $args)
        {
            $op = $this->getOperation($name);
            array_unshift($args, $this);

            return call_user_func_array([$op, 'execute'], $args);
        }

        /**
         * Returns an image in GIF or PNG format.
         *
         * @return string
         */
        public function __toString()
        {
            if ($this->isTransparent()) {
                return $this->asString('gif');
            } else {
                return $this->asString('png');
            }
        }

        /**
         * Returns a copy of the image object.
         *
         * @return WideImage_Image The copy
         **/
        public function copy()
        {
            $dest = $this->doCreate($this->getWidth(), $this->getHeight());
            $dest->copyTransparencyFrom($this, true);
            $this->copyTo($dest, 0, 0);

            return $dest;
        }

        /**
         * Copies this image onto another image.
         *
         * @param WideImage_Image $dest
         * @param int             $left
         * @param int             $top
         **/
        public function copyTo($dest, $left = 0, $top = 0)
        {
            if (!imagecopy($dest->getHandle(), $this->handle, $left, $top, 0, 0, $this->getWidth(), $this->getHeight())) {
                throw new WideImage_GDFunctionResultException('imagecopy() returned false');
            }
        }

        /**
         * Returns the canvas object.
         *
         * The Canvas object can be used to draw text and shapes on the image
         *
         * Examples:
         * <code>
         * $img = WideImage::load('pic.jpg);
         * $canvas = $img->getCanvas();
         * $canvas->useFont('arial.ttf', 15, $img->allocateColor(200, 220, 255));
         * $canvas->writeText(10, 50, "Hello world!");
         *
         * $canvas->filledRectangle(10, 10, 80, 40, $img->allocateColor(255, 127, 255));
         * $canvas->line(60, 80, 30, 100, $img->allocateColor(255, 0, 0));
         * $img->saveToFile('new.png');
         * </code>
         *
         * @return WideImage_Canvas The Canvas object
         **/
        public function getCanvas()
        {
            if ($this->canvas == null) {
                $this->canvas = new WideImage_Canvas($this);
            }

            return $this->canvas;
        }

        /**
         * Returns true if the image is true-color, false otherwise.
         *
         * @return bool
         **/
        abstract public function isTrueColor();

        /**
         * Returns a true-color copy of the image.
         *
         * @return WideImage_TrueColorImage
         **/
        abstract public function asTrueColor();

        /**
         * Returns a palette copy (8bit) of the image.
         *
         * @param int  $nColors      Number of colors in the resulting image, more than 0, less or equal to 255
         * @param bool $dither       Use dithering or not
         * @param bool $matchPalette Set to true to use imagecolormatch() to match the resulting palette more closely to the original image
         *
         * @return WideImage_Image
         **/
        abstract public function asPalette($nColors = 255, $dither = null, $matchPalette = true);

        /**
         * Retrieve an image with selected channels.
         *
         * Examples:
         * <code>
         * $channels = $img->getChannels('red', 'blue');
         * $channels = $img->getChannels('alpha', 'green');
         * $channels = $img->getChannels(array('green', 'blue'));
         * </code>
         *
         * @return WideImage_Image
         **/
        abstract public function getChannels();

        /**
         * Returns an image without an alpha channel.
         *
         * @return WideImage_Image
         **/
        abstract public function copyNoAlpha();

        /**
         * Returns an array of serializable protected variables. Called automatically upon serialize().
         *
         * @return array
         */
        public function __sleep()
        {
            $this->sdata = $this->asString('png');

            return ['sdata', 'handleReleased'];
        }

        /**
         * Restores an image from serialization. Called automatically upon unserialize().
         */
        public function __wakeup()
        {
            $temp_image = WideImage::loadFromString($this->sdata);
            $temp_image->releaseHandle();
            $this->handle = $temp_image->handle;
            $temp_image   = null;
            $this->sdata  = null;
        }
    }
